Prior art material handling systems include an overhead beam, such as an I-beam or a similar beam. A lower flange of the beam functions as a track on which the rollers of a trolley are engaged so that the trolley is translatable along the beam. The trolley is operatively connected to a load-carrying apparatus, such as a hoist or a block and tackle apparatus, to facilitate the transportation of heavy or cumbersome objects.
These prior art systems are sometimes described as “open-track” or “open-roller” because the flange of the beam, i.e., the track on which the trolley wheels are engaged, is exposed to the environment. The accumulation of dust and debris on the track may cause considerable resistance to the trolley rollers during trolley translation along the track. The resistance may be particularly problematic if the trolley is propelled manually. To alleviate this problem, newer material handling systems often employ enclosed track rails, in which a track and passage for a trolley are enclosed and therefore protected from the environment. The new enclosed track rails result in less resistance to the movement of the trolley, and have fewer maintenance requirements, than the prior art open-roller tracks. It is therefore desirable to replace open-roller tracks with enclosed track rails.
To avoid the cost of removing existing open-track beams and installing new support structure for new enclosed track rail, enclosed track rail is sometimes retrofitted to existing material handling systems by suspending the new track rail below an existing open-track beam with a hanger connected to the lower flange of the beam. However, retrofitting a material handling system by suspending an enclosed track rail from an existing beam substantially increases the vertical dimension of the material handling system, which correspondingly decreases overhead clearance beneath the material handling system. This problem is particularly acute where an existing beam is in a low-clearance area; in this instance, suspension of an enclosed track rail below the beam may be impractical or impossible because the enclosed track rail would be excessively low. Substantial cost must then be incurred in removing the existing beams and installing new support structure for the enclosed track rail.